Understanding Direct Boxes: Types

In Part 1 of our Understanding Direct Boxes series, we discussed the three primary functions that a direct box performs. Today, we will look at the two main types of direct boxes and how to use them.

Active vs Passive

There are two types of direct box: Active and Passive. The passive DI works standalone, you can plugin and get to work. The active DI employs a preamplifier stage that boosts levels and requires power. Most active direct boxes receive this power from one of three sources:

Batteries

External power supply

Phantom power (from the connected mixer)

Selection of the appropriate DI for the job can make the difference between good results and great results. This choice offers the savvy engineer another tool to optimize the gain structure of their system.

Conventional wisdom says:

Active source: Passive direct box

Passive source: Active direct box

Running a passive single coil guitar? Grab an active DI. Slapping a modern bass with active pickups? Reach for the passive DI. Because the active direct box contains an amplifier the weaker signal inputs will be boosted before entering the stage snake.

However, many designs like the Radial Engineering J48 Stereo can blur the lines between when to grab a passive or active DiI. Active DIs can be helpful for driving longer cable runs and they provide more headroom loud instruments. Making them a smart choice for keyboard instruments or track playback from a computer or smartphone.

Conclusion

As you can see knowing the difference between active and passive direct boxes can help in optimizing the performance from your sound system. In addition to simply connecting an instrument they can play an important role in getting a clean signal through your sound system.

Our recommendation is to invest in at least one of each and try them everywhere. There is no harm in trying them out. This will allow you to develop your own preferences about what to use with each instrument.